Warm weather, low rainfall causing cracks in Adelaide homes

HOMES in some of Adelaide's blue-ribbon suburbs are literally cracking at the seams.
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Katrina Stokes

The AdvertiserApril 24, 20133:35pm

HOMES in some of Adelaide's blue-ribbon suburbs are literally cracking at the seams.

The state's unseasonal warm weather, combined with below average rainfall in the past six to 12 months, is causing major headaches for tens of thousands of homeowners who are reporting cracks in their homes.

In the past three weeks, one building advisory group, Archicentre, has noticed a huge jump in calls from Adelaide residents seeking help for splitting walls - up from two a month to two a day.

Weather conditions, coupled with the city's infamous reactive clay soils - which is said to be among the worst in the world by experts - is the reason behind our cracking dilemma.

While Adelaide has seen some rainfall in the past few days, experts say it was not nearly enough to help repair our homes. They say we need sustained winter rain to help our parched soil.

Some experts warn cracking problems could only get worse as Australia - and the world - grapples with the extreme effects of drought and flooding caused by climate change.

Figures obtained from Archicentre reveal almost 50 per cent of homes inspected have cracking issues which, they say, is costing homeowners between $350 and $65,000 to fix.

Heritage homes in some of Adelaide's premier, leafy suburbs - including Wayville, Westbourne Park and Goodwood, where median house prices range between $620,00 and $800,000 - are in the state's worst-hit areas.

Data from Archicentre shows as many as eight in 10 homes in these suburbs have reported cracking problems.

Surrounding suburbs including Netherby, Kensington, Kingswood, Linden Park and Hectorville are also taking a hit. But why are these areas more prone to problems than others?

The buildings in these suburbs sit on highly reactive clay soil, which shrinks and reacts when moisture content changes.

Archicentre state manager Edward Lukac said homes built on dark brown or black clay are the areas most susceptible to cracking.

"If it's got clay in the mixture, it's susceptible to shrinking and cracking - particularly the older walls in homes," he said.

Mr Lukac said homes in the suburbs surrounding Newton, Hope Valley, Holden Hill, parts of Gilles Plains and Hillcrest were actually built on Adelaide's worst soil.

Despite this, many of the homes in these areas are relatively crack-free because they are newer residences which have been built on solid concrete foundations. "In these bad areas there tends to be a lot of newer homes (built in) the '60s and '70s when they started to use brick veneer on concrete slabs," Mr Lukac said.

"They have a better construction system."

IT'S a different story for Adelaide's eastern fringe, famous for its old, heritage-style sandstone and bungalow homes built more than 100 years ago.

"You get those older inner-city suburbs that are on clay-based soils which aren't as reactive, but because they've got brittle footing, they are susceptible to moving in different ways," Mr Lukac said.

"If you're in an old bungalow, the really old ones are sitting on stones that have been put together with cement ... each wall can move separately."

Sandy soil found on and near Adelaide's coast - including in the suburbs of Port Adelaide, Semaphore, Ottoway, Tennyson and Wingfield - are the safest areas from cracking.

"The water drains straight through it, so you don't get that movement that you get on clay," Mr Lukac said.

FMG Engineering director John Goldfinch, whose business is a member of the Housing Industry Association, said he had also seen a recent increase in the number of people worried about cracking.

"This time of year is what we call cracked-house season," he said.

"We are at the end of a long, hot, dry period.

"The drying causes unsettlement of footings and of house walls and that brings in the cracking."

Mr Goldfinch said the last time Adelaide had seen similar cracking conditions was in the "great drought" between 2006 and 2010.

"The homes most at risk are those on the old, bluestone foundations ... the homes in the inner-southern suburbs near the CBD are particularly bad areas for cracking."

He said significant and unregulated trees in these areas - often not permitted to be chopped down - had also caused moisture to be sucked out of homes.

"In dry periods of climate the demand of the tree roots of a significant tree effects soil-drying and hence, on settlements of houses that flows through to increased incidents of cracking," Mr Goldfinch said.

He said the old stone footings in most - if not all - of Adelaide's heritage homes were not strong enough to resist the soil movement caused by long periods of dry, hot weather.

Nowadays, homes are build differently.

But he said no home was 100 per cent safe from at least some form of cracking.

"With the modern reinforced concrete footings everything is tied together to crack as one, so you don't get cracking as well," he said.

Mr Goldfinch said regular watering was the easiest way Adelaide homeowners could try to prevent cracks from appearing.

"While we are permitted to do so, (you can) maintain your garden watering and don't neglect lawn watering," he said.

"It will help the soil not to know that is has actually stopped raining if we artificially put the rain in and water it."

He encouraged homeowners to install drip irrigation systems - the simplest and cheapest form of soil rehydration - which could save them from forking out tens of thousands of dollars in the future.

"It's economical on the use of water and it also maintains the soil moisture content so we stop the soil from drying out which in turns stops the house from cracking," Mr Goldfinch said.

"It's particularly useful in the old cottages around Parkside and Unley Park."

And, while engineers are doing everything in their power to build homes differently these days, Mr Goldfinch's crystal ball forecasts the state's cracking problem will only get worse.

"We are looking at long-term climate change," he said.

"Scientists are telling us we are going to see more droughts and more floods - they are the extremes of our climate (so) it's very difficult for engineers to deal with."

Until then, Mr Goldfinch said engineers were working towards new and improved ways to ensure the performance of houses could withstand whatever Mother Nature brings.